In the case of images with large geometric distortions, an orthorectification method may be necessary to reduce the distortion due to the relief or the viewing angle of the images. For a first order polynomial image registration model, a minimum of three reference points are required to calculate the model. For satellite imagery these reference point are known as ground control points (GCPs). In practice, it is usually better to use more than three reference points. However, it may not always be practical to obtain more than three reference points, for example, registration of satellite images of coastal and oceanic regions.
Present geometric registration methods use an affine transformation that requires more than three reference points. To determine the correct geometric registration of high spatial resolution images measured by multi-satellite sensors over the ocean, it is often desirable to use only images that include coastal regions. Still, even these methods may not be applicable for situations where there are few GCPs available, such as in oceanographic studies using satellite multi-sensor measurements, which often include significant cloud contamination. The difficulty of registering images is increased by the cloud contamination, as the presence of cloud cover that may occlude some of the GCPs in one or both of the images. Accordingly, it is desirable for improved registration methods aimed at studying images of oceanic regions, as well as land regions.
The present invention addresses this need among others.